In the previous chapter, we have already seen that in order to match a substring, you simply need to write the string inside a regular expression. For example, to match hello, you would create this variable:
var pattern = /hello/;
We also learned that if we want to match all occurrences of the string or character of the regular expression, we can use the g flag within Regex. However, situations where you have as clear a pattern like these are rare, and even when they come up, it's arguable whether
Regex is even required. You really see the true power of regular expressions when you have less concrete information.
There are two main features the Regex engine implements that allow you to correctly represent 80 percent of your patterns. We will cover these two main features in this chapter:
- Vague matchers
- Multipliers
In this topic, we will cover character classes that tell the Regex to match a single vague character. Among the vague matches, there can be a character, digit, or an alphanumeric character.
Let's say we wanted to find a sequence where we have 1, and then any other character followed by 3, so that it would include 123, 1b3, 1 3, 133, and so on. For these types of situations, we need to use a vague matcher in our patterns.
In the preceding example, we want to be able to use the broadest matcher possible; we can choose to put no constraints on it if we wish to and it can include any character. For these kind of situations, we have the . matcher.
A period in Regex will match any character except a new line, so it can include letters, numbers, symbols, and so on. To test this out, let's implement the aforementioned example in our HTML utility. In the text field, let's enter a few combinations to test the pattern against 123 1b3 1 3 133 321, and then for the pattern, we can specify /1.3/g. Running it should give you something similar to this:
The wildcard character is not the only character to match vague patterns, nor is it always the right choice. For example, continuing from the previous example, let's say that the character in between 1 and 3 is a number. In this case, we might not care which digit ends up there, all we have to make sure of is that it's a number.
To accomplish this, we can use a d. vague matcher The d backslash or digit special character will match any character between 0 to 9. Replacing the period with the backslash d character will give us the following results:
Only two out of the four matches mentioned earlier comply with the new constraint. The last main vague matcher is w, which is a
word character. It will match the underscore character, numbers, or any of the 26 letters of the alphabet (in both lowercase as well as uppercase letters). Running this in our app will give us the following results:
